Junction electronic

Moreover, the possibility of considering single-electron phenomena in a frame of a dot-based system theory allows consideration of even semiconductor nanoparticles as quantum dots, useful for single-electron junctions (Averin et al. 1991). 

Several experimental techniques were applied to characterize these objects. It was found that CdS was formed as small particles inside the LB film with sizes in the nanometer range. Similar work was carried out that resulted in the formation of PbS, CuS, HgS, etc. The sizes of the particles produced by such approaches turned out to be rather similar to that of CdS. The observed sizes suggest that the objects could be useful for the formation of nanogranules for room-temperature single-electron junctions. 

As the second step, the STM tip was locked over the desired particle, feedback was temporally switched off, and voltage-current (V-I) characteristics were measured. The typical trend of the V-I characteristics is shown in Figure 29. Current steps are clearly observable in the presented curve, indicating that the single-electron junction was formed. It is worth mentioning that the characteristics observed in areas without particles demonstrate a normal tunneling behavior (see Fig. 30). 

The approach described represents one more step toward the realization of a completely stand-alone single-electron junction based on nanoparticles and produced in organic matrix. Quantum dot synthesis directly on the tip of a metal stylus does not require the use of STM for localizing the particle position and requires only the use of atomically flat electrodes and a feedback system for maintaining a desirable double-barrier structure. 

Thus, previously described experiments had demonstrated the possibility of realization of single-electron junctions based on CdS nanoparticles. Nevertheless, because only one type of particle was tested, the question about the role of the material s properties for successful single-electron junction formation was still open. 

Apart from transistor-like devices, single-electron junctions can also be useful for sensor applications. The simplest one might be the monitoring of H2S. Since the formation of CdS nanogranules takes place when an initial cadmium arachidate layer is exposed to this gas, we can expect the appearance of single-electron conductivity only when it is present in the atmosphere. 

Apart from the described single-electron junctions, there is another exciting technological possibility for use of these nanoparticles. It turned out that the particles could be aggregated into very thin polycrystaUine layers (Facci et al. 1994a). We will now describe some aspects of this phenomenon. 

Summarizing, it is possible to conclude that the technique of forming ultrasmall semiconductor particles turned out to be a powerful tool for building up single-electron junctions, even working at room temperature, as well as thin semiconductor layers and superlattices with structural features, reachable in the past only via molecular beam epitaxy. 

Amines have been utilized to bind SAMs to gold surfaces and nanoparticles. Venkataraman et al. [197] found that in terms of molecular electronic junctions. 

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Molecular Electronic Junction Transport Some Pathways and Some Ideas... 

Fig. 1 Schematic representation of the most commonly used molecular electronic junctions ordered as a function of the number of contacted molecules...

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Figure 6.31 Schematic for HPLC-NMR coupling. ( ) direction of flow (—) electronic junctions (PSU) peak sampling unit (SPE) sohd phase extraction unit.

Figure 1.10 Schematic of the experimental set-up used for HPLC-NMR coupling BPSU, Bruker peak sampler unit (-) capillary junctions ( ) electronic junctions...

Figure 17.13 Structure formulas of V-shaped rotaxanes 144+ and 154+, and bistable rotaxanes 164+ and 174+, used to construct switchable electronic junctions for memory and logic function purposes.114 118 119 (Adapted with permission from V. Balzani et al., ChemPhysChem 2008, 9, 202-220. Copyright Wiley-VCH Verlag GmbH Co. KGaA.)...

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